Corundum is a crystalline form of aluminum oxide and is found in various different colors, most of which are generally referred to as sapphire. Sapphire is a hard and strong material with a hardness of 9.0 on the Mohs scale, and, as such, is capable of scratching nearly all other minerals. Because of its hardness and strength, sapphire may be an attractive alternative to other translucent materials like glass or polycarbonate. However, due to its brittle nature, sapphire is susceptible to dramatic strength reductions as a result of small defects in the surface or edge of the part. It is generally desirable to minimize small defects that may occur during manufacturing to produce a sapphire part that is durable and long lasting.
Manufacturing a near defect-free sapphire part may present unique challenges. The strength of a brittle material, such as sapphire, is limited due to flaw population on the surface or edges of the part. An inconsistent or inadequate surface or edge finish can lead to the propagation of micro cracks and result in a weakened part. Traditional translucent materials like silicate glass are able to be chemically strengthened to a significant depth to minimize the effect of these flaws, but on extremely hard materials such as sapphire, a similar process is not readily available. Additionally, sapphire's hardness makes cutting and polishing the material both difficult and time consuming when conventional processing techniques are implemented.